Vitamin B 12 deficiency is a common, but under diagnosed condition found primarily in the elderly. This deficiency mainly results from changes in the gastrointestinal tract that take place during aging and from certain medications. Untreated, this condition can lead to physical and mental impairment that significantly reduces the quality of life and increases health care expenditures. [unreadable] Current approaches to diagnose vitamin B 12 deficiency lack specificity, have poorly defined reference ranges and are expensive. Our objective is to fill the need for a low cost, accurate and simple test. Metabolic Solutions, Inc. (MSI) has developed a breath test based on the principle that the metabolism of propionate is limited by the availability of vitamin B12. Thus, after orally administering a tracer dose of 13C (non-radioactive) labeled propionate the amount of 13CO2 appears less intensely in the breath of vitamin B12 deficient individuals as compared to those individuals with normal B12 status. During phase I, we plan to demonstrate that the breath test distinguishes adequate from deficient vitamin B12 individuals and that the breath test changes with treatment. [unreadable] Early screening and prompt diagnosis of vitamin B12 deficiency will prevent devastating complications. A small window of opportunity exists to reverse neurological complications. Any delay in instituting treatment may result in little or no improvement in cognitive function. Providing physicians with an accurate, low cost tool for diagnosing vitamin B12 deficiency will not only improve patient care but is cost-effective because once identified this condition can be successfully and inexpensively treated. [unreadable] [unreadable]